Guided wave radar level transmitter uses guided wave radar (GWR) technology. Based on the reflection of microwave on the surface medium. Through the probe, continuous level measurement of liquid and solid levels is completed.

Guided wave radar level transmitter

A guided wave radar level transmitter is also called a wave-guided radar level sensor. They can measure both levels and the interface between two media. Through probe rod or cable, complete level contact types continuous level measurement. Such as Coaxial Probe Guided Wave Radar Level Transmitter. This is different from ultrasonic level measurement, which is non-contact measurement. A guided wave radar level transmitter is often used for tank level measurement. Including liquid and solid. Output 4~20mA/HART, so as to measure and control the level during production.

Sino-Inst offers a variety of Guided wave radar Level Transmitters for industrial level measurement. If you have any questions, please contact our sales engineers.

We also supply level transmitters, like: Pressure Level Transmitter; Submersible Level Transmitter; and (DP) level transmitter

Features of Guided Wave Radar Level Transmitters

Features of Guided Wave Radar Level Transmitters
  • Using advanced microprocessors and unique echoDiscovery echo processing technology, the guided wave radar level sensor can be used in a variety of complex conditions.
  • A variety of process connections and types of detection components, guided wave radar level sensor for a variety of complex conditions and applications. Such as high temperature, high pressure, etc.
  • With the pulse working mode, the guided wave radar level meter has very low transmitting power. And can be installed in various metal and non-metal containers without harm to the human body and the environment.

Customer benefits:

  • Microwaves are unaffected by temperature, pressure, specific gravity and vapors
  • Easy to install
  • No moving parts
  • Ignores light continuous coatings
  • Good for vacuum service
  • More direct energy return – more consistent signal
  • Built-in waveform screen (Scope Trace)

Industries served:

  • Oil and gas production
  • Refining
  • Pharmaceutical and biotech
  • Power generation
  • Pulp and paper
  • Iron and steel
  • Chemicals
  • Food and beverage
  • Marine

Parameters of SIRD70 Guided wave radar level transmitters

General Parameters

Probe Material:

  • Rod                                               Stainless Steel 316L/PTFE
  • Cable                                            Stainless Steel 316L/PTFE
  • Coax                                             Stainless Steel 316L/PTFE
  • Seal                                              Viton fluororubber , Kalrez Fluorinated rubber 
  • Process Connection                     Stainless Steel 316L
  • Shell                                             Stainless Steel 316L, Plastic,Aluminum
  • Ground  Terminal                          Stainless Steel 316L

Power: 2-Wire   

  • Standard Version                           (16~26)V DC
  • Intrinsic Safe Version                    (21.6~26.4)V DC
  • Power Consumption                      max. 22.5mA
  • Ripple Allowed
    • – <100Hz                                        Uss < lV
    • – (100~100K)Hz                            Uss < l0mV

Flameproof Type

  • (22.8 ~ 26.4) V DC       2-wire system
  • (198 ~242)V AC   4-wire system / 110V AC    4-wire system
  • Power Consumption                                  max. 1VA,1W


  • Output Signal                               (4~20)mA/HART
  • Resolution                                    1.6μA
  • Failure mode                                20.5mA;22mA;3.9mA, hold
  • 2-wire load resistance                  See the diagram below
  • 4-wire load resistance                  Max.500 ohm
  • Integration Time                           ( 0~36)sec, adjustable
Parameters of SIRD70 Guided wave radar level transmitters
SIRD70 guided wave radar level transmitters
SIRD70 guided wave radar level transmitters

Specifications of Guided Wave Radar Level Transmitters

Max Measurement Distance 701         30m/6m(Cable /Rod)
702         20m/6m(Cable /Rod)
703         30m/6m(Cable /Rod)
704           6 m
705         15m/6m(Cable /Rod)
Measurement Interval           About 1sec (Depend on parameter settings)
Adjustment Time                About 1sec (Depend on parameter settings)
Resolution of Display  1mm
Accuracy             ±10mm(See the accuracy illustration diagram below)
Temperature for Storage/Transport               (-40~80) ℃Process Temperature  (Probe)  
701、704       (-40~250)℃
702            (-40~200)℃
703            (-40~130)℃
705            (-200~400)℃
Relative Humidity   <95%  
Pressure         Max. 40MPa
Vibration Proof  Mechanical vibration 10m/s² , (10~150)Hz

guided wave radar level transmitter data sheet

Guided wave radar level transmitter range


H— Measuring range

L—Empty distance

B—The top of the blind

E—The minimum distance from the probe to the tank wall

–Blindspot is the minimum distance between the top of the highest material surface materials and the measurement reference point.

–The bottom of the blind refers to a distance near the very bottom of the cable that can not be accurately measured.

–Between the top and bottom of the blind is blind effective measure distances. 

Guided wave radar level transmitter range


In order to ensure the accuracy of level measurement, the material should be located between the top and bottom of the blind.

Measuring Range:

The following table lists the relationship between different types of measured media and measurement distance.

Media DK(ε)Solid particlesLiquidMeasuring range
11.4~16-Condensation gas, such as N2CO23m (only refers to the coaxial rod probe)
21.6~19-Plastic with particles
-White limestone, special cement
-Liquefied petroleum gas, such as propane
-Freon 12/ Freon
-Palm oil
31.9~25-Ordinary cement, gypsum-Mineral oil, fuel30m
42.5~4-Cereals, seeds
-Benzene, styrene, toluene
54~7-Wet stones, ores
-Chlorobenzene, chloroform
-Cellulose spray
-Isocyanide hydrochloric acid, this amine
6>7-mineral powder
-Carbon black
-Aqueous liquid
-Liquid ammonia

Extended reading: Radar Level Meter for Corrosive Liquids

What is guided wave radar?

Micropower impulse radar (MIR) combines time domain reflectometry (TDR), equivalent time sampling (ETS), and modern low power circuitry.

This synthesis of technologies creates a high-speed Guided Wave Radar (GWR) transmitter.

The electromagnetic pulses are propagated via a waveguide, that focuses the energy and yields a system, many times more efficient than Non-Contact Radar (Non-contact radar level transmitters).

Time domain reflectometry (TDR)

TDR uses pulses of electromagnetic (EM) energy to measure distances or levels.
When a pulse reaches a dielectric discontinuity (such as one created by a media surface), a portion of the pulse is reflected.
The greater the dielectric difference between air and the process medium being measured, the greater the amplitude of the reflection.

Equivalent time sampling (ETS)

ETS, or Equivalent Time Sampling, is used to measure the high speed, low power EM energy.
ETS is a critical key in the application of TDR to vessel-level measurement technology.
The high-speed EM energy (1000 ft/us) is difficult to measure over short distances, and at the resolution required in the process industry.
ETS captures the EM signals in real time (nanoseconds), and reconstructs them in equivalent time (milliseconds), which is much easier to measure with today’s technology.

Guided-wave radar (GWR) level transmitter working principle

Levelflex works with high-frequency radar pulses, which are emitted and guided along with the probe.

As the pulse meets the medium surface, part of the emitted pulse is reflected due to a change of the dc value (relative dielectric constant).

The Time-of-Flight between pulse launching and receiving is measured, and analyzed by the instrument and constitutes a direct measure for the distance, between the process connection and the product surface.

install for guided wave radar level transmitter
Install for guided wave radar level transmitter

Waveguides can be metal rigid rods or flexible metal cables. The microwave pulse travels down the outside of the rod or cable. It is reflected on the surface of the material to be tested, and the echo is received by the antenna. The propagation distance can be calculated from the time difference between the launch and echo pulses.


  • Compared with ultrasonic and radar level gauges, the work is stable and reliable;
  • Like radar level gauges, the strength of the reflected signal depends on the dielectric or conductivity of the material being measured. However, the guided wave type can measure materials with lower dielectric constants.
  • It has a strong ability to suppress steam and foam, and the measurement is not affected;
  • Not affected by liquid density, looseness of solid materials, temperature, and dust during feeding;
  • Low maintenance, high performance, high precision, high reliability and long service life.


  • Double rods (cables) and coaxial tubular waveguides are easily affected by external structures due to the concentration of electric field energy;
  • It is easy to accumulate material between the rods (or inside the tube), resulting in false echoes and affecting the measurement effect;
  • The cable buried in the material will generate a large pull-down force due to the gravity of the material, causing the cable to be pulled off and other failures.

Extended reading: Features Of Magnetostrictive Level Transmitters

The microwave pulse emitted by the high frequency radar level transmitter is transmitted through the antenna, while the guided wave radar level transmitter is transmitted through the detection component.

So, is the installation standard of the guided wave radar level transmitter the same as that of the high-frequency radar level transmitter?

Today, let’s take a look at the installation standards of guided wave radar level transmitters.

  1. Try to avoid the facilities in the tank during installation, and avoid the detection components (steel cables or steel rods) contacting internal obstacles during the measurement process, which will affect the measurement accuracy.
  2. When installing, try to keep the detection component perpendicular to the surface of the measured medium. In this way, the microwave pulses sent out can reach the designated position, and the later data can be accurate.
  3. During installation, the guided wave radar level transmitter should keep a certain distance from the container wall, and should be kept away from the feed and discharge ports. The feed and discharge ports have a great influence on the accuracy and stability of the guided wave radar level transmitter, so attention must be paid.
  4. If the guided wave radar level transmitter is threaded, its length should not exceed 15mm. Generally, the length of the thread is inversely proportional to the stability of the measurement, that is, the shorter the thread, the more stable the measurement.
  5. During installation, if the cable is too long, we need to cut off the power supply of the guided wave radar level transmitter, remove the cable, and remove the screw on the heavy hammer, and then intercept it from the bottom of the cable.
  6. During installation, if the guided wave radar level transmitter is installed in the still-pipe, pay attention to fix the radar probe with an insulating bracket to ensure that the probe and the still-pipe are concentric, so as to avoid vibration caused by improper installation and affect the accuracy of the measurement.
  7. When installing the guided wave radar level meter, if the connection surface of the container is made of other materials than metal, either use a metal flange to connect, or configure a metal plate.

The above are the main installation standards of the seven-point guided wave radar level transmitter summarized by Sino-Inst. In fact, the standard of guided wave radar level transmitter is far more than that.

When installing, be sure to read the manual of the self-contained product in detail. If you have any questions, you can contact the manufacturer’s engineer.

The relative permittivity of a medium is a physical quantity that characterizes the polarization of the medium.

It is determined by the properties of the medium itself.

Therefore, different media have different relative permittivity.

The dielectric constant of the measured medium directly affects the reflectivity of the high-frequency pulse signal.

When an electromagnetic pulse hits the surface of a medium, the electromagnetic wave is reflected and refracted.

The larger the relative permittivity, the smaller the reflection loss. On the contrary, the smaller the relative permittivity, the greater the transmission loss and the more serious the signal attenuation.

When the conductivity of the measured medium is greater than 10mS/cm, all of them will be reflected back. That is, the stronger the echo signal.

The signal will be extremely attenuated due to too small relative permittivity. Therefore, each guided wave radar level gauge has a minimum relative permittivity to ensure that the radar level gauge can be used normally.

Different companies’ guided wave radar liquid level transmitters have different structural designs and different requirements for minimum relative permittivity.

What is the difference between radar and ultrasonic level transmitter?

Radar liquid level sensors and ultrasonic liquid level sensors are non-contact liquid level measuring instruments. They mainly differ in the following three aspects:

Working principle

  1. Ultrasonic level sensor
    The ultrasonic level sensor uses non-touch measurement method. It is suitable for liquid level measurement in water conservancy and hydrology, chemical petroleum and sewage treatment. The probe of the ultrasonic level sensor is also called a transducer. The transducer emits ultrasonic pulses to the object to be measured. After touching the surface of the medium, the sound wave is reflected by the surface of the medium and is received by the transducer again. The time from when the sound wave is emitted to when it is absorbed and consumed after reflection will be proportional to the distance between the transducer and the medium.
  2. Radar level sensor
    Radar level sensors also use non-touch measurement methods. The measuring principle is similar to that of an ultrasonic level sensor. That is, the antenna emits electromagnetic waves, and the electromagnetic waves are reflected back after reaching the measured liquid surface. Then the antenna receives and recognizes the time distance that Baud has.


The time consumed by the ultrasonic storage and analysis of the sound waves in each period of the ultrasonic level sensor is slightly longer. For this reason, if the rate of liquid level change is too fast, it is generally not recommended to use an ultrasonic level sensor. In addition, the ultrasonic level sensor is sensitive to misty vapor and fine dust within the area. Therefore, ultrasonic level sensors are not suitable for high-pressure and high-temperature environments, misty spaces filled with vapor, or spaces with dust. But on the contrary, the radar level sensor can prevent the disturbance of the above-mentioned environment.

Cost performance

The market price of ultrasonic level sensors produced in China usually ranges from one thousand yuan to several thousand yuan. The appearance of its products is more delicate than that of radar level sensors, so transportation costs will be reduced accordingly. In comparison, the structural design of the radar level sensor is more messy and the measurement steps are more refined, so the price is higher. Especially when the user needs a radar level sensor with HART protocol, the unit price is more expensive. But now the price gap is not big, and it is shrinking year by year.

Through induction and comparison, it is not difficult to find that the ultrasonic level sensor and the radar level sensor have their own advantages and disadvantages. Therefore, it is recommended that users should consider many aspects when purchasing liquid level timing. It is not only necessary to meet the preset specifications, but also to scientifically include the above aspects into consideration.

Extended reading: Ultrasonic Oil Level Sensor-External Paste-Truck Fuel Tank

Maybe you still have questions like:

How to calibrate radar level transmitter?

What’s the guided wave radar level transmitter principle of operation?

You can just contact us for more information about GWR level transmitters.

Our guided wave radar (GWR) level transmitters, are made in China,

With better price, and higher quality.


Guided wave radar devices, also called wave-guided radar level transmitters.
Have no moving parts and require minimum maintenance.
They can measure both levels and the interface between two media.
The guided wave radar level sensor is applied to water storage tanks,
acid and alkali storage tanks, slurry storage tanks,
solid particles, and small oil storage tanks.
All kinds of conductive, non-conductive media, corrosive media.
Such as coal bunkers, ash silos, oil tanks, acid tanks, etc.

Radar level transmitters use radar technology to perform the non-contact continuous level measurement. The radar level indicator converts the level into an electrical signal. The level signal output can then be utilised by other instrumentation to monitor or control. Liquids and solids are commonly measured with this measuring technique. Like: Fly ash silo. Radar level sensors are divided into: Pulsed radar technology and frequency modulated continuous wave (FMCW) radar level sensors.
Extended reading: Radar level sensor for solids – Dust solid level measurement

The main factors affecting the price of guided wave radar level sensors are: Type of medium. Explosion-proof requirements, material and size, temperature, output signal, interface type. Connection method, etc. The reference price is 500-900USD.

Guided wave radar is a measuring instrument based on the principle of time travel. The radar wave travels at the speed of light, and the running time can be converted into a level signal by electronic components.
The instrument measures the distance from the reference point to the material surface. The probe sends out high-frequency pulses and propagates along the cable. When the pulses meet the material surface, they are reflected back and received by the receiver in the instrument. The time signal is converted into a material level signal.

GWR level transmitter is guided wave radar level transmitter. GWR level transmitter is an instrument based on guided wave radar to measure level.

Straighten the wave guide cable, place an internal obstacle with a radius of 30cm, put a vise (simulate the liquid level), and use a steel ruler with high precision to compare the error and calculate the accuracy.

The above method is not very accurate.
If possible, it can be installed on the tank, and the dipstick can be compared.

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Sino-Inst offers over 10 GWR Corrosive Liquid Chemical Level Sensors for level measurement. About 50% of these are Guided Radar level meters, 40% is the tank level sensor.

A wide variety of GWR Corrosive Liquid Chemical Level Sensors options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Guided Wave radar level measurement instrumentation, located in China.

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